Clamping and articulation element

ABSTRACT

A two-piece clamping element comprises two separate, i.e., non-integral, opposing first and second clamping jaws forming a laterally open cavity to receive a pin or rod-shaped element. Each clamping jaw has a bore aligned with one another to receive a screw, wherein a pivot bearing is arranged opposite said cavity allowing the two opposing clamping jaws to come in contact to one another. The pivot bearing comprises at least one set of complementary part-cylindrical bearing surface portions. An anti-rotation pin extends between the two jaw members.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from European Patent ApplicationNo. EP 06 110 244.8 filed on Feb. 21, 2006, the disclosure of which ishereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

The invention pertains to a clamping element for the clamping of arod-shaped element of an articulation element, particularly a clampingelement, of an articulation element for the stabilization of bonefractures. The invention also pertains to an articulation element withtwo clamping elements and with one at least two-piece locking device,and optionally an anti-rotation device.

U.S. Patent Publication 2003/0181911 describes a single-piece clampingelement with two opposing cavities and one laterally open cavity toreceive a clamping jaw forming a rod-shaped element and a hinge, whichis arranged opposite the cavity, connecting the clamping jaws so thatthey are movable on top of each other, with each clamping jaw having onebore each aligned flush with one another.

This clamping element has the advantage that an articulation can beproduced with two identical clamping elements arranged next to oneanother, inserting a connecting screw through the bore, which is screwedinto an internally threaded nut to close the clamping jaws.

From U.S. Pat. No. 5,752,954 an articulation is known consisting of twotimes two individual clamping jaw elements and one central screw. Thisarticulation allows the lateral insertion of one or two rod-shapedelements into the corresponding cavities. U.S. Pat. No. 5,752,954 has aspring, which spring tension allows the clipping in of the rod-shapedelements and holding the jaw elements on the rod-shaped elements beforethe articulation element is blocked. U.S. Pat. No. 6,616,664 providesfor narrow lateral lever arms to hold laterally inserted rod-shapedelements before the articulation is blocked. U.S. Pat. No. 6,342,054 hasan external spring.

SUMMARY OF THE INVENTION

Based on this state of technology, it is one role of the invention athand to provide a two-piece clamping element which allows the lateralinsertion of a rod-shaped element and which, when utilized dually, isdirectly applicable as an articulation element. It is another object ofthe invention to obtain a two-piece clamping element with advantages ofa single-piece clamping element, e.g. the working connection of the twoclamping jaws.

Another goal of the invention is the creation of a cost-effectivedisposable clamping element, particularly made of a synthetic material(such as plastic) injection molding, which does not have the structuraldisadvantages of X-ray transparent clamping elements as in U.S.Publication 2003/0181911. Especially it is an object of the invention torealize a disposable clamping element being able to support and transmitlarge pressure forces.

Based on the known state of technology, another role of the invention isalso to provide an improved articulation element. Such an improvedarticulation element is shown in U.S. Patent Publication 2006/0039750assigned to the assignee of the present invention.

A two-piece clamping element is provided comprising two separatenon-integral opposing first and second clamping jaws forming a laterallyopen cavity to receive a rod-shaped element, with each clamping jawhaving a bore aligned with one another.

A pivot bearing is arranged opposite the cavity bringing the twoopposing clamping jaws in contact to one another and thereby making themmovable towards and away from one another. Each clamping jaw has a bore,aligned with one another. The bores are arranged between the cavity andthe pivot bearing.

A first clamping jaw has an anti-rotation device on its exterior or areceptacle for receiving an anti-rotation device.

An articulation element can be formed from two clamping elements inwhich the clamping elements are arranged on top of one another withtheir first clamping jaws adjacent one another. The articulation elementhas one at least two-piece locking shaft with a first part of thelocking shaft insertable through a bore of the second clamping jaw ofone clamping element, and with a second part of the locking shaftinsertable through a bore of the first clamping jaw of the otherclamping element. One or the other or both parts of the locking shaftbeing able to be brought in contact with one another through the boresin the first clamping jaws. The first and second clamping jaws of theclamping elements can be blocked with the locking device. Thearticulation element has an anti-rotation device is arranged between thefirst clamping jaws that are arranged on top of one another, theanti-rotation device having a central bore. The anti-rotation device ispreferably a plate whose material is preferably harder than the materialof the clamping elements and which has ridges formed on both sides ofthe plate. The anti-rotation device can also be a cylinder whosematerial in a floor and a lid area thereof is preferably harder than thematerial of the clamping elements, and which preferably consists of aflexible, compressible material in the solid material part, inparticular synthetic foam. The locking device includes a cylindricalscrew and a conical nut, the conical nut preferably has a stop shoulderfor a self-locking screw, which can be inserted in an internal thread inthe cylindrical screw. A hollow spring enveloping the locking device isused as an anti-rotation device or as an additional anti-rotationdevice.

By equipping the two-piece clamping elements with functionally differentfirst and second clamping jaws, two clamping elements can be placed ontop of one another each with their first clamping jaws, to form anarticulation element in a simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Now the invention is more closely described with reference to thedrawings and with the aid of a number of embodiments:

FIG. 1 shows a perspective view of an articulation element with twoclamping elements per a first embodiment of the invention,

FIG. 2 shows a different perspective view of the articulation element ofFIG. 1,

FIG. 3 shows a cross-section view of the articulation element of FIG. 1or 2,

FIG. 4 shows a perspective view of an articulation element with twoclamping elements per a second embodiment of the invention,

FIG. 5 shows a different perspective view of the articulation element ofFIG. 4,

FIG. 6 shows a cross-section view of the articulation element of FIG. 4or 5,

FIG. 7 shows a top view of an anti-rotation device for an articulationelement per FIG. 1 or 4,

FIG. 8 shows a perspective view of another anti-rotation device for anarticulation element, and

FIG. 9 shows a partially sectioned lateral view of a part of a lockingscrew, a nut and a self-locking bolt for an articulation element per oneof the FIG. 1 to 6.

DETAILED DESCRIPTION

FIGS. 1 to 3 show a first embodiment of an articulation element with twoclamping elements 10 per the invention. FIGS. 1 and 2 show twoperspective views at different angles from the top. The two-partclamping element 10 has two clamping jaws 12 and 13 creating togetherone cavity 11 to receive a rod-shaped element. The cavity 11 is formedby transversely running grooves 14. The outer edges 16 of the sidefacing clamping jaws 12 and 13 are slanted to simplify the lateralinsertion of a rod-shaped element. Across from the cavity 11 and theslanted outer edges 16, a pivotal bearing 17 is arranged, comprisingcomplementary pivotal surfaces comprising semi-cylindrical portions 36and complementary grooves 38 contacting clamping jaws 12 and 13.

When the clamping element 10 is intended for a rod with 4 to 6millimeters in diameter, the opening at the free ends has a diameter of,for instance, 2 millimeters in a resting position. If the clampingelement 10 is intended for a rod with a diameter of 12 millimeters, theopening at the free ends has a diameter of, for instance, 9 millimetersin a resting position.

In the upper area of the clamping jaw 12 the area between cross ribs 21has been excluded with the exception of a round screw receptacle 23.Screw receptacle 23, for instance, has a conical shoulder area or a stepshoulder, whose purpose will be described later, which merges into acontinuous bore in the top clamping jaw 12, which can be seen in FIG. 3.

In the lower clamping jaw 13 cross ribs 21 end in a ring flange 22,which, for instance, may have a flat recessed ring shaped step, where aweight and material saving recess advantageous for injection molding canbe connected, with a bore in the center.

This continuous bore is aligned flush with the abovementioned bore intop clamping jaw 12. At the clamping element 10, it runs vertically tothe axis of the cavity 11. The bore is cylindrical and in its interior,it may have guide ribs arranged in regular intervals. Of course, thenumber of guide ribs may be chosen freely, preferably between three orfive ribs.

One clamping element 10 with the jaw parts 12 and 13 comprises asemi-cylindrical portions 36 running over the whole width of the jaw 12and being directed to a complementary groove 38 in jaw 13. The stops 36and 38 may be chosen shorter or in smaller portions with intermediateregions; however, the shown embodiment providing for a long pivotalbearing 17 is preferred. The stops 36 and 38 are running parallel to thecavity 11. Between the stops 36 and 38 and the vertically oriented boresfor the screw is provided a pin 136 and a corresponding reception bore138. The pin 136 can be seen in the cross-sectional view of FIG. 3,entering with play into the reception bore 138, to ensure that the jaws12 and 13 are not rotating one against the other and to allow an easyintroduction of a larger rod into the cavity 11 whereas thecomplementary stop surfaces 36 and 38 can loose contact but are guidedby elements 136 and 138. The pin 136 can be symmetrical in view of hismain axis but is preferably oblong in the transverse direction, e.g.parallel to surfaces 36 and groove 14.

FIGS. 4 to 6 show a second embodiment of an articulation element withtwo clamping elements 20 per the invention. FIGS. 4 and 5 show twoperspective views at different angles from the top. The two-partclamping element 20 has two clamping jaws 12 and 13 creating togetherone cavity 11 to receive a rod-shaped element. All identical or similarfeatures have received the same reference numerals as cavity 11 andgrooves 14. Across from the cavity 11, a pivotal bearing 17 is arranged,comprising complementary pivotal surfaces comprising semi-cylindricalportions 36 and complementary grooves 38 contacting clamping jaws 12 and13.

One clamping element 20 with the jaw parts 12 and 13 comprises twosemi-cylindrical portions 36 running on the left and on the right sideof a passage 238 of the jaw 12 and being directed to two complementarygroove portions 38 on both sides of a blocking pin 236 in jaw 13. Thestops surfaces 36 and 38 may also be chosen shorter; however, the shownembodiment providing for two rather long pivotal bearing surfaces 17 ispreferred. The blocking pin 236 and the corresponding reception bore 238are provided on the outer open side of the jaws 12 and 13. The pin 236is—seen from above—rectangular to ensure that the jaws 12 and 13 of theclamping element 20 can not rotate one against the other.

In the first embodiment of FIG. 1 to 3 the pin 136 is provided in thejaw 12 whereas in the second embodiment of FIG. 4 to 6 the blocking pin236 is provided in the jaw 13. This clearly shows that the features ofthe two embodiments can be mixed, the blocking pin 236 of FIG. 4 can beused within jaw 12 and the pin 136 of FIG. 1 can be used within jaw 13with the complementary bores in the other jaws 13 and 12, respectively.However, the represented embodiments are preferred.

A spiral or coil spring 119 is arranged between the two clampingelements 10 or 20, which is supported by the spring receptacle 121. Thespring receptacle 121 can form a hemispherical area; it can also belevel and smooth; in particular, it can be rough to ensure a greaterresistance of the spring 119 against twisting. The spring 119 pushes thetwo clamping elements 10 or 20 away from one another and is intended tosecure the twisting of the two clamping elements 10 or 20 against oneanother. It does not secure the forcing apart of the jaws 12 and 13;they open against the forces acting upon the clipping in of the rods 101and 102 in a radial direction with respect to grooves 14. The spring 119can also be a disk spring package or another resilient element.

FIG. 7 shows a top view of an anti-rotation device 90 for anarticulation element per FIG. 1. Anti-rotation device 90, for instance,is a thin metal plate with a central bore 91, a hub 92 and spokes 93.The outer rim 94, for instance, has successive punctured ridges 95 andrecesses 96. For instance, they are arranged so that recesses 96 arealways arranged opposite the six spokes 93 in this case, with each ofthe ridges 95 located intermittently.

It is clear that, a simple punching process to manufacture the plates ofthe anti-rotation device 90 is used, that ridges 95 seen from above arerecesses seen from below. Punctured ridges 95 and recesses 96 can beround, pyramidal or polygon shaped. They can run radially side by sidein several rows, in a larger number than in FIG. 7 etc. In anotheralternate design, radial ribs can be used as well.

The anti-rotation device 90 is to be positioned between the two clampingelements 10, 20 at the position 190 as indicated in FIG. 1, 2, 4 and 5.FIG. 3 and 6 show that an anti-rotation device can also be achievedthrough the design of the material of the first clamping jaw 13,comprising rough elements to avoid rotation between the contacting jaws13.

The anti-rotation device can also be a flexible synthetic foam element199 as per FIG. 8. Only upon the tightening of screw 103 theanti-rotation device 199 interlock and determine the angle position ofthe articulation element.

This is a flexible cylindrical element 199 with a central bore 198 forreceiving screw 103. It can be used in the place of an anti-rotationdevice 90. The advantage is that its material on the bottom and lidsurfaces 197 is harder and, in particular, can also be structured orspan hard inserts to engage in a ring-shaped step. The clamping element10 is then designed similar to the embodiment per FIG. 1, only the depthand the sidewalls are intended to receive the anti-rotation device 199.In the cylinder area, the element 199 is flexible to be compressed whenscrew 103 is tightened. The anti-twisting device is beveled and hasconical slants 196 between the surface 195 and the lid or the floor area197.

It is advantageous that the material in the floor and lid area of theanti-rotation device 199 is harder than the material of the clampingelements utilized, and in the solid material preferably consists of aflexible, compressible material, particularly synthetic foam.

The diameter of the anti-rotation device 90 or 199 is 30 millimeters andthe contact surface (radial width) for the outer rim 94 is 3millimeters. Instead of placing the ridges on element 90, the structures(ridges) can also be integrated in the material of the clamping jaw 13,for instance radial grooves.

FIG. 9 shows a screw 103 which is to be inserted through the alignedbores, which can sit on the conical screw receptacle 23 with its conicalflange 104. For tightening, screw 103 for instance has a square drivehead 105. It is clear that instead of a square, a hexagon or a slit etc.can be utilized. Preferably, the shoulder 104 is designed to becomplementary to the receptacle 23. A nut 106 is attached from the otherside. The nut 106 has a slightly conical sleeve 107 and a conical flange108 as a covering cap. The shape of flange 108 corresponds to the shapeof screw receptacle 23 of clamping element 10 or 20. The sleeve 107 isinserted into one bore and, to the best advantage, protrudes into theother bore and/or through it. The sleeve 107 is fitted in the press fit;additionally, it can also have an external thread. It can be designed asa fit for one of the internal threads used in bore.

In another design version, not illustrated in the drawings, a clampingelement is equipped with a tilting, but torsion rigid, bearing for thenut. The clamping jaw 12 again has the conically opening bore. Thisbore, however, has a recess on the side facing away from the cavity 11,which can be a rectangular slit in particular. During the assembly, thecylindrical nut is inserted in the recess. A tolerance exists throughthe cylindrical nut, so that when a rod 102 is clipped into cavity 11the top part 12 of the clamping element can be tilted as well. In orderto ensure the fixation of screw 103 and to design the nut torsionallyrigid, it has an appendage or projection, which protrudes into the saidrecess with lateral tolerance. In a lateral view of the clampingelement, the projection has a tolerance in the recess to permit thetilting motion of top part 12. In addition to the nut with projection,other design versions are possible, for instance, an L-shaped flattenednut, which, for example, has wobble rivets and is punched, so that anappendage protrudes into a corresponding nut in top part 12 and producesthe torsion rigidity.

The nut 106 has an internal thread that fits the complementary externalthread of screw 103. Through the tightening of screw 103 opposite nut106, the two clamping elements 10 and 20 are pulled together. Then, byexerting pressure, a rod can be inserted laterally in the respectivecavity. Since the diameters of the rods are larger than the opening atthe free ends, it is protected from falling out. Through a roughening ofgrooves 14, not illustrated in the drawings, it is also protected from asimple longitudinal displacement.

If screw 103 is tightened further, clamping jaws 12 and 13 are movedcloser towards one another against the resetting force of the hingebearing 17 and are finally completely blocked in their angled positionthrough the use of the plate of anti-rotation device 90 placed betweenthe clamp elements. At the same time, this fully secures the rods ingrooves 14 against longitudinal displacement as well as against twistingby minimizing the cavity 11. While self-locking screw 109 is notillustrated, it can be utilized here as well. Preferably the nut 106 isdesigned as a continuous sleeve.

When screw 103 is opened, nut 106 remains in the one clamping element.The anti-rotation device 90 has impressed itself into the softermaterial of jaw 13. Said impression makes it preferable—with theexception of an immediate tightening of the screw in this or anotherplace of an external fixator clamping element used for the samepatient—to use said clamping element only once and to throw it awayafter use. The material used for the clamp may be PEEK (Poly EstherEther Ketone), and may have chopped carbon fiber reinforcement for extrastrength. This allows the two pieces of the polymeric clamp to beinjection molded. The pressed in traces of the anti-rotation device inthe step is a sign of use for the clamping element, so that the user cansee that the reuse of the product can be excluded.

In the resting position of the clamping elements 10 and 20, clampingjaws 12 and 13 urged together by the spring force and the distance ofthe slit 27 is reduced. When screw 103 is tightened, the slit isminimized. Through the central transfer of force via the screw and nutelements 104 and 108 on the identical areas, the slit 27 is minimized inits thickness until the groove 14 contacts the rod in the cavity 11.Then the (upper) clamping jaw 12 with the ribs 21 deviates around therod and the semi-cylindrical region 36 touches down on the complementaryarea 38. When screw 103 is tightened further, the blocking effect setsin as of this time and the unit semi-cylindrical region 36—complementaryarea 38 takes over the bearing function.

Instead of a screw 103, another locking device can be used, for instancea clamping lever or a bayonet catch.

It is emphasized that the term embodiment in the previously mentioneddescription does not mean that only the elements described with respectto the respective clamping element or articulation element are subjectof the invention. In particular, these are also combinations of thecharacteristics described in objects of various embodiments and FIGS.For instance, a clamping element is an object of the invention, whichhas the bore and nut per FIG. 3, a counter nut 109 per FIG. 9 andnon-skid elements 99 for the rods per FIG. 8 or a part thereof. Acorresponding articulation element can be comprised of any two randomabove-mentioned clamping elements, if they can be utilized for theselected anti-rotation device.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A two-piece clamping element comprising two separate opposing first and second clamping jaws forming a laterally open cavity to receive a rod-shaped element, with each clamping jaw having a bore aligned with one another, wherein a pivot bearing is arranged opposite said cavity allowing the two opposing clamping jaws to come in contact to one another, wherein the pivot bearing comprises at least one set of complementary bearing surfaces portions.
 2. The clamping element as set forth in claim 1, wherein the set of complementary pivot bearing surfaces portions comprise part-cylindrical protrusion portions and complementary part-spherical grooves.
 3. The clamping element as set forth in claim 1, wherein a rotation avoiding pin is provided in one of the jaws whereas a corresponding similar reception bore for the rotation avoiding pin is arranged in the other of the jaws.
 4. The clamping element as set forth in claim 3, wherein the rotation avoiding pin is provided between the complementary bearing surfaces portions and cavity.
 5. The clamping element as set forth in claim 3, wherein the rotation avoiding pin is arranged such to divide the complementary bearing surfaces portions in two side parts.
 6. The clamping element as set forth in claim 1, wherein a first clamping jaw has an anti-rotation device on its exterior or a receptacle for receiving an anti-rotation device.
 7. An articulation element having first and second clamping elements as set forth in claim 1, which clamping elements are arranged on top of one another with their first clamping jaws adjacent one another, and having an at least two-piece locking device with a first part of the locking shaft insertable through a bore of the second clamping jaw of the first clamping element, and with a second part of the locking device insertable through a bore of the first clamping jaw of the second clamping element, and with one or the other or both parts being able to be brought in contact with one another through the bores in the first clamping jaws, and where the first and second clamping jaws of the first and second clamping elements can be blocked with the locking device.
 8. The articulation element as set forth in claim 7, wherein an anti-rotation device is arranged between the first clamping jaws that are arranged on top of one another, the anti-rotation device having a central bore.
 9. The articulation element as set forth in claim 8, wherein the anti-rotation device is a plate whose material is harder than the material of the clamping elements and which has ridges formed on both sides of the plate.
 10. The articulation element as set forth in claim 8, wherein the anti-rotation device is a cylinder whose material in a floor and a lid area is preferably harder than the material of the clamping elements, and which consists of a flexible, compressible material in the solid material part, in particular synthetic foam.
 11. The articulation element as set forth in claim 8, wherein a hollow spring enveloping the locking device is used as an anti-rotation device or as an additional anti-rotation device.
 12. A two-piece clamping element for an external bone fixation system comprising: a first piece having a bore therethrough and a rod or pin receiving opening extending from an external surface of the first piece, the first piece having an arcuate pivot bearing surface open to the external surface and an anti-rotation element associated with the external surface; a second piece having a bore therethrough alignable with the bore in the first piece and a rod or pin receiving opening extending from an external surface of the second piece, the external surface of the second piece having an arcuate pivot bearing surface and an anti-rotation element associated therewith engageable with the arcuate pivot bearing and anti-rotation element of the first piece when the external surfaces of the first and second pieces are juxtaposed.
 13. The two-piece clamping element as set forth in claim 12, wherein the complementary pivot bearing surface on the first and second pieces comprise part-cylindrical protrusions and complementary part-spherical grooves.
 14. The two-piece clamping element as set forth in claim 13, wherein each part-cylindrical protrusion and groove have a central axis extending parallel to a central longitudinal axis of the rod or pin receiving opening.
 15. The two-piece clamping element as set forth in claim 12, wherein the anti-rotation element on the first piece is an integrally formed pin element extending from the external surface thereof and the anti-rotation element on the second piece is a recess open to the external surface thereof for receiving the pin.
 16. The two-piece clamping element as set forth in claim 15, wherein the anti-rotation pin and recess are centrally located between two side surfaces of each of the first and second pieces.
 17. The two-piece clamping element as set forth in claim 16 wherein the part-cylindrical protrusion and groove are located adjacent both of the two side surfaces of the first and second pieces.
 18. An articulation element for an external bone fixation system comprising two clamping elements as set forth in claim 12 having a locking pin extending through aligned bores of each clamping element and a spring element located around the pin between the two clamping elements.
 19. The articulation element as set forth in claim 18 further comprising a means for preventing the relative rotation of the two clamping elements about the locking pin.
 20. The two-piece clamping element as set forth in claim 12 wherein the first and second pieces are made of a molded polymeric material. 